1. Field of the Invention
The present invention relates to a temperature measuring method for measuring the temperature of an infrared-transmitting semiconductor substrate such as a silicon substrate with a radiation thermometer, and an apparatus therefor.
2. Related Background Art
In the manufacturing process of semiconductor devices such as IC chips, it is necessary to anneal a semiconductor substrate such as a silicon substrate after ion implantation thereto With the recent use of heating apparatus capable of annealing within a period of several tens of seconds with radiation, in order to prevent diffusion of impurities, it is required to measure the substrate temperature within a short time and to control the heating temperature
For this purpose, the temperature has been determined by:
(1) measurement with a thermocouple; or
(2) measurement of the spectral radiation of the substrate with a radiation thermometer and calculation with the known Planck's equation based on the measured radiation and the emissivity of the substrate measured in advance.
However the method (1) is associated with the drawbacks of eventual contamination caused by the mounting of the thermocouple on the surface of the substrate, and of difference between the surface temperature of the substrate and temperature measured by the thermocouple.
Also the method (2) is incapable of precise temperature measurement, because the emissivity varies from substrate to substrate according to the doping concentration thereof, and also varies with the rise in temperature of the substrate. For example, in case of a silicon substrate, the emissivity in the middle infrared range at normal temperature is almost zero for a low doping concentration, but reaches 0.5 or even higher at a high doping concentration. Also the emissivity increases rapidly with the rise in temperature of the substrate.